"By boat you can reach Mälaren, Köping or Arboga in the west, or Västerås, Eskilstuna or Stockholm if you drive east. We direct our search in all these directions".
He told the Swedish television channel, SVT: "I have talked to a person at the county administrative board that says that it is not possible to put an economic value on this, these are invaluable objects of national interest".
An eyewitness, Tom Rowsell, said: "One of my friends saw two people running ... I saw the boat just there, a white little boat with a motor on the back.
"The two men hurriedly jumped on board. We contacted the police and told them and they told us they had taken something from the Cathedral."
Royal Central.co.uk says the two crowns were for King Karl IX and Queen Kristina from 1611.